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  • 51.
    Malmström, Mikael
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. Uppsala University, Sweden.
    Tarasenko, Oleksandr
    Margulis, Walter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. Acreo Swedish ICT AB, Dept Fiber Photon, Stockholm, Sweden.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    All-Fiber Nanosecond Gating for Time-Resolved Spectral Analysis2016In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 28, no 8, p. 829-832Article in journal (Refereed)
    Abstract [en]

    We demonstrate the addition of time gating to a standard optical spectrum analyzer (OSA) operating in the spectral region similar to 1.06 mu m. This is accomplished by opening for 7 ns the optical input to the OSA with an electrically driven poled fiber in a Sagnac loop. The sequential interrogation with nanosecond resolution of the reflection from three fiber Bragg gratings along a piece of fiber allows distinguishing the spectral peaks created with a minimum separation of 85 cm. The passive extinction ratio of this device is >40 dB and returns to >40 dB from >23 dB on a 35-ns time scale directly after time gating.

  • 52.
    Marinins, Aleksandrs
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Knudde, Nicolas
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Air-Suspended SU-8 Strip Waveguides With High Refractive Index Contrast2016In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 28, no 17, p. 1862-1865Article in journal (Refereed)
    Abstract [en]

    Integrated polymer photonics is efficient and cheap solution for many applications, such as optical communications and sensors. Waveguides are basic elements of photonic integrated circuits, and their performance directly influences optical circuit efficiency. However, it is a challenge to develop small footprint polymer waveguides with reasonable losses due to low refractive index comparing to cladding. In this letter, we present free-standing SU-8 waveguides with high refractive index contrast. SiO2 cladding is selectively etched, leaving only air as a cladding material; waveguides are supported by thin pillars. Removal of SiO2 cladding eliminates light leakage to substrate and provides better light confinement. Straight and bending SU-8 waveguides are numerically simulated and experimentally verified lambda = 1550 nm. We also report reduced propagation and bending losses in discussed waveguides.

  • 53.
    Marinins, Aleksandrs
    et al.
    KTH, School of Engineering Sciences (SCI).
    Ozolins, O.
    Pang, X.
    Udalcovs, A.
    Navarro, J. R.
    Kakkar, Aditya
    KTH, School of Engineering Sciences (SCI).
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI).
    Jacobsen, G.
    Popov, Sergei
    KTH, School of Engineering Sciences (SCI).
    Thermal Reflow Engineered Cylindrical Polymer Waveguides for Optical Interconnects2018In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 30, no 5, p. 447-450Article in journal (Refereed)
    Abstract [en]

    Integrated polymer photonics brings low cost and high fabrication flexibility to optoelectronic industry. However, this platform needs to overcome several issues to be effective enough for practical applications. In this letter, we experimentally demonstrate a decrease of propagation losses and polarization sensitivity of polymer waveguide-based devices as a result of thermal treatment. Heating of poly(methyl methacrylate) strip optical waveguides above the glass transition temperature initiates a waveguide surface reflow due to a decrease of the polymer viscosity and surface tension energy. This results in a decrease of surface roughness and shape change from rectangular to cylindrical. Thus, scattering losses and polarization sensitivity are minimized. 

  • 54.
    Myrén, Niklas
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Margulis, Walther
    Acreo.
    All-fiber electrooptical mode-locking and tuning2005In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 17, no 10, p. 2047-2049Article in journal (Refereed)
    Abstract [en]

    Active mode-locking of a fiber laser with an all-fiber electrooptic modulator is demonstrated. A 1.4-V driving signal was used, creating subnanosecond single pulses at the fundamental frequency of the cavity (12 MHz). The modulator was a packaged Mach-Zehnder interferometer incorporating a poled twin-hole fiber in one of the arms. The switching voltage was 230 V at 1550 nm, with extinction ratio similar to 20 dB. The interferometer could be electrooptically tuned by 3.5 nm.

  • 55.
    Myrén, Niklas
    et al.
    Acreo.
    Margulis, Walther
    Acreo.
    Ortega, B.
    Acreo.
    Puerto, G.
    Acreo.
    Pastor, D.
    Acreo.
    Capmany, J.
    Acreo.
    Li, J.
    Acreo.
    Belmonte, M.
    Acreo.
    Pruneri, V.
    Acreo.
    Systems measurements of 2x2 poled fiber switch2005In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 17, no 12, p. 2571-2573Article in journal (Refereed)
    Abstract [en]

    The performance of a 2x2 all-fiber electrooptical switch is characterized in a system at up to 40 Gb/s. Error-free transmission is demonstrated. The device was also employed as a protection switch at 10 Gb/s in an installed fiber link.

  • 56.
    Nilsson, S.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Kjellberg, T.
    Klinga, T.
    Wallin, J.
    Streubel, K.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    DFB laser with nonuniform coupling coefficient realized by double-layer buried grating1993In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 5, p. 1128-1131Article in journal (Refereed)
    Abstract [en]

    A technique for the realization of a nonuniform grating coupling coefficient kappa , and its implementation in distributed-feedback (DFB) lasers is presented. This technique, which is an extension of the buried-grating concept, offers precise control of the coupling coefficient and enables a kappa -ratio greater than 10. DFB lasers with an asymmetric kappa -variation have been fabricated using this method. A front-to-rear facet output power ratio close to five was obtained, qualitatively in agreement with simulations.<>

  • 57.
    Pang, Xiaodan
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Ozolins, Oscar
    Gaiarin, S.
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Rodrigo Navarro, J.
    Iglesias Olmedo, M.
    Schatz, Richard
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Udalcovs, A.
    Westergren, U.
    Zibar, D.
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Experimental Study of 1.55-μ m EML-Based Optical IM/DD PAM-4/8 Short Reach Systems2017In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 29, no 6, p. 523-526, article id 7839925Article in journal (Refereed)
    Abstract [en]

    We experimentally evaluate high-speed intensity modulation/direct detection (IM/DD) transmissions with a 1.55-μ text broadband electro-Absorption modulated laser and pulse amplitude modulations (PAM). We demonstrate 80 Gb/s/ λ PAM-4 and 96 Gb/s/ λ PAM-8 transmissions with low-complexity digital equalizers at the receiver. Performance comparison with different types of equalizers are performed, including linear symbol-spaced feed-forward equalizer (FFE), fractional (half-symbol) spaced FFE and decision feedback equalizer (DFE), with different tap number. It is found that for both cases, a 6-Tap symbol-spaced FFE is sufficient to achieve a stable performance with bit-error-rate below the 7% overhead hard decision forward error correction (7%-OH HD-FEC) threshold over a 4 km standard single mode fiber link. Practical considerations including comparison between adaptive and static equalizer implementation and tolerable fiber chromatic dispersion are discussed.

  • 58. Pfrommer, H.
    et al.
    Piqueras, M. A.
    Herrera, J.
    Polo, V.
    Martinez, A.
    Karlsson, S.
    Kjebon, Olle
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics.
    Yu, Y.
    Tsegaye, I.
    Liu, C. P.
    Chuang, C. H.
    Enard, A.
    Van Dijk, F.
    Seeds, A. J.
    Marti, J.
    Full-duplex DOCSIS/wirelessDOCSIS fiber-radio network employing packaged AFPM-based base-stations2006In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, no 04-jan, p. 406-408Article in journal (Refereed)
    Abstract [en]

    The simultaneous wireline (600 MHz) and wireless (5.5 GHz) transmission of data over cable service interface specification (DOCSIS) signals in a hybrid fiber-radio access network is presented. The DOCSIS signal wireless replica is generated by means of an optical harmonic up-conversion technique based on a dual-drive Mach-Zehnder modulator. The optical signal is fed to a base station (BS) where a packaged asymmetric Fabry-Perot modulator/detector acts simultaneously as a photodetector and an optical modulator. At the BS, the DOCSIS signals can be fed either to a wireline or a wireless access network, in a highly flexible approach. Full-duplex operation has been demonstrated for both access types, including indoor wireless transmission.

  • 59. Pougeoise, E.
    et al.
    Gilet, P.
    Grosse, P.
    Grenouillet, L.
    Chelnokov, A.
    Gerard, J. -M
    Bouillard, J. -S
    Lerondel, G.
    Blaize, S.
    Vilain, S.
    Bachelot, R.
    Royer, P.
    Hamelin, R.
    Berggren, Jesper
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Sundgren, Petrus
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Experimental study of the lasing modes of 1.3-ÎŒm highly strained InGaAs-GaAs quantum-well oxide-confined VCSELs2009In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 21, no 6, p. 377-379Article in journal (Refereed)
    Abstract [en]

    We present an experimental study of the main modes involved in the emission properties of InGaAs-GaAs quantum-well oxide-confined long wavelength vertical-cavity surface-emitting lasers. Lasing properties are dominated by the so-called "oxide modes" and by aperture modes, respectively, for small and large driving currents. We present complementary investigations of the laser emission including far-field angular distribution and spectroscopic near-field optical microscopy to a better understanding of the nature of the "oxide modes."

  • 60. Prawiharjo, Jerry
    et al.
    Gallo, Katia
    Optoelectronics Research Centre, University of Southampton (UK).
    Thomsen, Ben
    Roelens, M.
    Almeida, Paulo
    Broderick, Neil
    Richardson, David
    Frequency-Resolved Optical Gating in a Quasi-Phase-Matched LiNbO3 Waveguide2005In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 17, no 4, p. 849-851Article in journal (Refereed)
    Abstract [en]

    We demonstrate the complete characterization of short pulses around 1.55 mu m by cross-correlation frequency-resolved optical gating based on sum-frequency generation in an integrated LiNbO3 device. Excellent retrieval is achieved for pulsewidths ranging from 30 to 4 ps.

  • 61. Ren, Guobin
    et al.
    Shum, Ping
    Nanyang Techbological University, Singapore.
    Zhang, Liren
    Yan, Min
    Nanyang Techbological University, Singapore.
    Yu, Xia
    Tong, Weijun
    Luo, Jie
    Design of all-solid bandgap fiber with improved confinement and bend losses2006In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, no 24, p. 2560-2562Article in journal (Refereed)
  • 62.
    Rodrigo Navarro, Jaime
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO. Acreo Swedish, Sweden.
    Pang, Xiaodan
    Kakkar, Aditya
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Ozolins, Oskars
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Jacobsen, Gunnar
    Popov, Sergei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Adaptive Boundaries Scheme for Cycle-Slip Mitigation in C-mQAM Coherent Systems2015In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 27, no 20, p. 2154-2157Article in journal (Refereed)
    Abstract [en]

    We propose a method for cycle-slip mitigation in circular multilevel quadrature amplitude modulation (C-mQAM) coherent optical systems, with constellation rotational asymmetry, based on an adaptive boundaries approach. The impact of cycle-slips in C-mQAM coming from Viterbi-Viterbi algorithm limits the phase noise tolerance. By introducing adaptive boundaries and a differential coding scheme, the ambiguity of asymmetrical rotation of constellation can be effectively removed. Performance of the proposed method is evaluated for a C-16QAM and C-64QAM for various laser linewidths. Results show a noticeable improvement in linewidth symbol duration product (Delta(upsilon) . T-S) tolerance compared with the previous studies on C-mQAM and mQAM constellations. The Delta(upsilon) . T-S tolerance reaches 4 x 10(-4) and 1.1 x 10(-4) for C-16QAM and C-64QAM, respectively, for 1 dB penalty at a symbol error rate of 10(-3).

  • 63.
    Rugeland, Patrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Sterner, Carola
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Margulis, Walter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Monolithic Interferometers Using Gemini Fiber2011In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 23, no 14, p. 1001-1003Article in journal (Refereed)
    Abstract [en]

    Gemini fibers are used to fabricate monolithic interferometers. The thermal stability of a monolithic Michelson interferometer is found to be superior to that of a conventional fiber ribbon interferometer. The fabrication of fused couplers, fiber Bragg gratings, and a broadband Mach-Zehnder add-drop multiplexer are demonstrated using the novel fiber.

  • 64.
    Rugeland, Patrik
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Yu, Zhangwei
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tarasenko, Oleksandr
    Tengstrand, Göran
    Margulis, Walter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tunable photonic microwave generation based on a novel dual-polarization fiber laser cavity2011In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 23, no 24, p. 1878-1880Article in journal (Refereed)
    Abstract [en]

    A novel dual-polarization fiber laser is proposed by incorporating a distributed feedback grating inscribed in a twin-hole fiber with internal electrodes. Dual-polarization lasing is achieved with a spectral separation of 42 pm. By beating the optical waves at a photodiode, a microwave signal at 5.244 GHz is achieved with a signal-to-noise ratio 45 dB. An electrically tuned microwave signal with a tunable range of 150 MHz is demonstrated.

  • 65.
    Saavedra, A. A.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Rigole, P. -J
    Goobar, E.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Nilsson, S.
    Amplitude and frequency modulation characteristics of widely tunable GCSR lasers1998In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 10, p. 1383-1385Article in journal (Refereed)
    Abstract [en]

    The amplitude (AM) and frequency (FM) modulation responses of a grating assisted codirectional coupler with rear sampled grating reflector laser were measured over a 40-nm tuning range. The extracted modulation bandwidth varied between 3 and 4 GHz and parameters as parasitic cutoff, maximum relaxation frequency and K-factor were extracted from curve fittings to the AM response. The frequency modulation measurements revealed low chirp despite the large tunability of the device. The linewidth enhancement factor was calculated from the AM and FM measurements. The values ranges from three to nine for ten different operating wavelengths

  • 66.
    Saavedra, A. A.
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Rigole, P. -J
    Goobar, E.
    Schatz, Richard
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Nilsson, S.
    Relative intensity noise and linewidth measurements of a widely tunable GCSR laser1998In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 10, p. 481-483Article in journal (Refereed)
    Abstract [en]

    The intensity and frequency noise of a grating assisted codirectional coupler with rear sampled grating reflector laser with 40-nm tuning range and 35-dB sidemode suppression ratio (SMSR) have been measured. The linewidth varies from 430 kHz to 4 MHz as a function of tuning. The resonance frequency, intrinsic bandwidth and damping factor for this device were extracted from the relative intensity noise (RIN) measurements. At high bias, the RIN is -150 dB/Hz and the maximum resonance frequency is 4.5 GHz

  • 67.
    Schatz, Richard
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Berglind, Eilert
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Gillner, Lars
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Parameter extraction from DFB lasers by means of a simple expression for the spontaneous emission spectrum1994In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 6, p. 1182-1184Article in journal (Refereed)
    Abstract [en]

    A simple expression for the amplified spontaneous emission from a laser biased below lasing threshold is applied to semiconductor laser parameter extraction. We demonstrate that accurate measurement of the coupling coefficient for distributed feedback (DFB) lasers with phaseshifts and end reflections is a practical possibility. It is also shown that the used expression, for a reciprocal device, can be derived directly from the wave equation using the Green’s function.<>

  • 68. Shao, L. Y.
    et al.
    Lau, S. T.
    Dong, X. Y.
    Zhang, A. P.
    Chan, H. L. W.
    Tam, H. Y.
    He, Sailing
    High-frequency ultrasonic hydrophone based on a cladding-etched DBR fiber laser2008In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 20, no 5-8, p. 548-550Article in journal (Refereed)
    Abstract [en]

    Distributed-Bragg-reflector (DBR) fiber-laser-based ultrasonic hydrophone has been found to possess increased detectable frequency range due to the improved sensitivity in the high-frequency region when the fiber cladding thickness was reduced. A wet etching technique is utilized to reduce the fiber diameter of the DBR laser. The peak response frequency moves from 21 to 40 MHz when the fiber diameter was reduced from 125 to 68 mu m.

  • 69. Shao, Li-Yang
    et al.
    Dong, Xinyong
    Zhang, A. Ping
    Tam, Hwa-Yaw
    He, Sailing
    High-resolution strain and temperature sensor based on distributed Bragg reflector fiber laser2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 17-20, p. 1598-1600Article in journal (Refereed)
  • 70. Shao, Li-Yang
    et al.
    Zhang, A. Ping
    Liu, Wei-Sheng
    Fu, Hong-Yan
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Optical refractive-index sensor based on dual fiber-Bragg gratings interposed with a multimode-fiber taper2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 1, p. 30-32Article in journal (Refereed)
  • 71.
    Shi, Yaocheng
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Anand, Srinivasan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    A polarization-insensitive 1310/1550-nm demultiplexer based on sandwiched multimode interference waveguides2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 21-24, p. 1789-1791Article in journal (Refereed)
    Abstract [en]

    A polarization-insensitive dual-wavelength demultiplexer based on sandwiched multimode interference waveguides is presented. Polarization-insensitive multimode waveguides are achieved first by choosing a suitable refractive index of the SiNx middle region. The demultiplxing function is then realized by adjusting the width and length of the multimode region. Simulation results obtained from three-dimensional beam-propagation method show that the demultiplexer can work at 1310- and 1550-nm bands for both polarizations simultaneously with a low insertion loss and a broad bandwidth.

  • 72.
    Shi, Yaocheng
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Dai, Daoxin
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Novel ultracompact triplexer based on photonic crystal waveguides2006In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, no 21-24, p. 2293-2295Article in journal (Refereed)
    Abstract [en]

    Two stages of directional couplers based on photonic crystal waveguides Are cascaded to form an ultracompact triplexer. The directional couplers are decoupled at the wavelength of 1310 rum. The length of the coupling region in the first directional coupler is chosen to separate the other two wavelengths (i.e., 1490 and 1550 nm), and the coupling region is tapered to improve the extinction ratios. The second directional coupler separates the wavelengths of 1490 and 1310 run. For the channel of 1550 nm, an additional directional coupler is used to reduce the crosstalk from the channels of 1490 and 1310 nm. The total size of the present triplexer is only 50 mu m x 20 mu m, and the good performance is verified with finite-difference time-domain simulation.

  • 73.
    Shi, Yaocheng
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Dai, Daoxin
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Proposal for an ultracompact polarization-beam splitter based on a photonic-crystal-assisted multimode interference coupler2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 9-12, p. 825-827Article in journal (Refereed)
    Abstract [en]

    An ultracompact polarization-beam splitter (PBS) combining a multimode interference (MMI) coupler and some photonic crystal (PC) structures is presented. The MMI coupler is designed to collect polarized powers reflected by or transmitted through an internal PC sturcture. The simulation result shows that the designed PBS is very short (about 50 mu m), and has a low insertion loss, a high extinction ratio, and a broad bandwidth.

  • 74. Shi, Z. M.
    et al.
    He, J. J.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Waveguide echelle grating with low polarization-dependent loss using single-side metal-coated grooves2004In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, no 8, p. 1885-1887Article in journal (Refereed)
    Abstract [en]

    A novel type ofechellegroove, in which only the illuminated facet is coated with metal, is proposed for the design of a planarwaveguideechellegrating. Numerical simulations using the rigorous coupled-wave analysis show that the metal coating on the shaded facet of a conventional metallicechellegratingis the main source of thepolarization-dependentloss(PDL) while it does not contribute to the improvement of the diffraction efficiency. It is also shown that the diffraction efficiency, especially for the transverse-magnetic mode, is enhanced and the PDL is greatly reduced when the proposedsingle-sidemetallic coating is used.

  • 75. Soderberg, Emma
    et al.
    Gustavsson, Johan S.
    Modh, Peter
    Larsson, Anders
    Zhang, Zhenzhong
    Berggren, Jesper
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Suppression of higher order transverse and oxide modes in 1.3-mu m InGaAsVCSELs by an inverted surface relief2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 08-maj, p. 327-329Article in journal (Refereed)
    Abstract [en]

    It is shown, by a systematic variation of design parameters, that the use of an inverted surface relief is very effective for suppressing higher order transverse modes in oxide confined 1.3-mu m InGaAs vertical-cavity surface-emitting lasers (VCSELs). Single-mode emission is achieved for a large variety of oxide aperture and surface relief diameters, with optimum designs, having a surface relief with a diameter half of that of the oxide aperture, producing 1.1-1.3 mW of single-mode power. It is also shown that the anti-phase layer employed to enable the use of an inverted surface relief is effective for suppressing oxide modes that otherwise appear in oxide confined VCSELs with a large detuning between the gain peak and the cavity resonance.

  • 76. Soh, D. B. S.
    et al.
    Codemard, C.
    Wang, Shunhua
    KTH, Superseded Departments, Physics.
    Nilsson, J.
    Sahu, J. K.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    Philippov, V.
    Jeong, Y.
    Alegria, C.
    Baek, S.
    A 980-nm Yb-doped fiber MOPA source and its frequency doubling2004In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, no 4, p. 1032-1034Article in journal (Refereed)
    Abstract [en]

    A continuous-wave (CW) master oscillator-power amplifier (MOPA) fiber source, tunable around 978 run, was frequency-doubled to 488.7 nm. Both the laser and the amplifier were made with cladding-pumped jacketed air-clad Yb-doped fibers. The MOPA generated up to 2.7 W of power in an output beam with an M-2 value of 1.8. This was frequency-doubled in a periodically poled potasium titanyl phosphate crystal at room temperature, in a single-pass configuration. The generated blue light had a CW power of 18.1 mW, a nearly Gaussian spatial intensity profile, and an M-2 value of 1.7.

  • 77. Song, J.
    et al.
    Wang, L.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, J. J.
    Effect of volume defects on the performance of planar waveguide devices2005In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 17, no 11, p. 2322-2324Article in journal (Refereed)
  • 78.
    Song, Jun
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhu, Ning
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    High Sensitive Gas Sensor Application Based on a Small Defect in Silicon Waveguide2009In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 21, no 1-4, p. 82-84Article in journal (Refereed)
    Abstract [en]

    A small defect in silicon nanowire waveguides is applied for gas sensors. Small defects with some special shapes and indexes can produce strong resonances with the incident light and induce large loss. Since the silicon waveguide has air cladding, the position of resonant peaks will be sensitive for the variation of the ambient air composition. The sensor based on the principle has a high sensitivity. As an example, we monitored the change of the position of the resonance peak as a function of alcohol concentrations in air. Results showed that a similar to 5-mg/L ethanol vapor in the air can result in a similar to 20-nm wavelength shift of the resonance.

  • 79.
    Song, Jun
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhu, Ning
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Jian-Jun
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Echelle grating demultiplexers with reduced return loss by using chirped diffraction order design2006In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, no 14, p. 1506-1508Article in journal (Refereed)
    Abstract [en]

    A design for echelle grating demultiplexers is presented to reduce the return loss. The input waveguide is placed on the minimal intensity position of the diffraction envelope. Then, by further chirping the diffraction order for each facet, we minimize the envelope intensity for other adjacent diffraction orders, which can contribute to a negligible return loss for a large spectral width. The present design is appropriate for multifrequency laser or multistage demultiplexer applications.

  • 80.
    Song, Jun
    et al.
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Zhu, Ning
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    He, Jian-Jun
    State Key Laboratory of Modern Optical Instrumentation, Zhejiang University.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Etched diffraction grating demultiplexers with large free-spectral range and large grating facets2006In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, no 24, p. 2695-2697Article in journal (Refereed)
    Abstract [en]

    A design for etched diffraction grating demultiplexers is presented to obtain both large grating facets and a larger free-spectral range (FSR) using the optimal chirped diffraction orders for different facets. The large grating facets by using a large diffraction order contribute to lowering the manufacturing difficulty, and can provide lower polarization-dependent loss. However, usually the large diffraction order must lower the FSR of the device by all means. Based on the present design, the FSR can overlay the whole diffraction envelop for a special order, but avoid the influence of the adjacent diffraction envelops. Calculations indicate that the extinction ratio between the operated order and adjacent orders can attain a 35 dB or so, which makes the crosstalk from channels in adjacent envelops to those in the operated diffraction envelop acceptable.

  • 81.
    Sudirman, Azizahalhakim
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    Margulis, Walter
    KTH, School of Engineering Sciences (SCI), Applied Physics, Quantum Electronics and Quantum Optics, QEO.
    All-Fiber Optofluidic Component to Combine Light and Fluid2014In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 26, no 10, p. 1031-1033Article in journal (Refereed)
    Abstract [en]

    A component is presented that combines light and fluid in an optical fiber arrangement for optofluidics. The component couples light from a standard telecom fiber (STF) to the solid-core of a microstructured fiber, and delivers fluid from a capillary to the holes of the same microstructured fiber. The light is then made to interact longitudinally with the delivered fluid in a hollow-core fiber or capillary. The component is all-spliced, hermetic and allows for fluid flow without interrupting the optical beam. Light is brought from the STF to the solid-core/fluid interface with a loss <0.1 dB.

    Download full text (pdf)
    All-Fiber Optofluidic Component to Combine Light and Fluid
  • 82.
    Sun, Xu
    et al.
    KTH, School of Information and Communication Technology (ICT).
    Chen, Xi
    KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Yan, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Thylen, Lars
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    All-Optical Switching Using a Hybrid Plasmonic Donut Resonator With Photothermal Absorber2016In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 28, no 15, p. 1609-1612Article in journal (Refereed)
    Abstract [en]

    A novel hybrid plasmonic (HP) donut resonator integrated with a photothermal plasmonic absorber has been developed, which can be used as a compact all-optical switch or modulator. The radius of the fabricated HP donut resonator is 1.8 mu m, with a resonant wavelength around 1550 nm and a quality factor (Q factor) around 600. The photothermal plasmonic absorber is directly integrated above the HP device, which can absorb as much as 75% of impinging optical power at 1064 nm wavelength. Since the absorber is in tight contact to the Si ridge of the HP waveguide, the absorbed optical power can efficiently heat up the Si ridge, and hence change the resonant wavelength of the HP donut resonator by Si thermal expansion effect. Experimental results show that the power used for 15 dB amplitude switch is only 10 mW, with rise and fall response times around 18 and 14 mu s, respectively.

  • 83. Taccheo, S.
    et al.
    Sorbello, G.
    Laporta, P.
    Karlsson, G.
    Laurell, Fredrik
    KTH, Superseded Departments, Physics.
    230-mw diode-pumped single-frequency er: yb laser at 15 mu m2001In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 13, no 1, p. 19-21Article in journal (Refereed)
    Abstract [en]

    We report on a diode-pumped Er:Yb laser able to generate a single-frequency output power in excess of 200 mW at both 1.53 mum and 1.56 mum and over 300 mW in multimode operation. The tuning characteristics of the source are reported and discussed, The relative intensity noise presents in all configurations a peak value lower than -92 dB/Hz and its level decreases below - 160 dB/Hz for frequencies higher than 8 MHz.

  • 84.
    Tang, Yongbo
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Dai, Daoxin
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Proposal for a Grating Waveguide Serving as Both a Polarization Splitter and an Efficient Coupler for Silicon-on-Insulator Nanophotonic Circuits2009In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 21, no 1-4, p. 242-244Article in journal (Refereed)
    Abstract [en]

    A grating waveguide is introduced and designed to serve as both a polarization splitter and an efficient vertical coupler between a fiber and a silicon-on-insulator (SOI) nanophotonic waveguide. Through this grating waveguide, the light from the fiber can be efficiently coupled into an SOI chip where the two orthogonally polarized waves are separated to travel towards the opposite directions along the waveguide. According to our simulations, the optimized structure can give a high coupling efficiency of about 50% for both polarizations, as well as a large bandwidth of over 70 nm and a very low polarization crosstalk below -22 dB at the output ports.

  • 85.
    Tarasenko, Oleksandr
    et al.
    Acreo Swedish ICT, Sweden.
    Margulis, Walter
    Acreo Swedish ICT, Sweden.
    The effect of the electrode curvature on the field in internal electrode fibers2015In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 99, p. 1-3Article in journal (Refereed)
    Abstract [en]

    By solving the two-dimensional Poisson equation for fibers with circular internal electrodes, we show that the parallel-plate approximation incurs significant error in the determination of the electric field applied to the fiber core. This also affects the value of chi((3)) measured in electro-optical fibers. The exact solution of Poisson's equation is used to solve the field applied to the core of a photonic crystal fiber, where the many holes screen the field. A universal curve is derived to allow using the simplifying parallel plate approximation and correcting for the error in symmetric fibers with round holes.

  • 86. Tarraf, A.
    et al.
    Riemenschneider, F.
    Strassner, Martin
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Daleiden, J.
    Irmer, S.
    Halbritter, H.
    Hillmer, H.
    Meissner, P.
    Continuously tunable 1.55-mu m VCSEL implemented by precisely curved dielectric top DBR involving tailored stress2004In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, no 3, p. 720-722Article in journal (Refereed)
    Abstract [en]

    We present an optically pumped and continuously tunable 1.55-mum vertical-cavity surface-emitting laser (VCSEL). The device shows. 26-mn spectral tuning range, 400-muW maximum output power, and 57-dBm side-mode suppression ratio. The VCSEL is implemented using a two-chip concept. The movable top mirror membrane is precisely designed to obtain a tailored air-gap length (L' = 16 mum) and a radius of curvature (ROC = 4.5 mm) in order to efficiently support the fundamental optical mode of the plane-concave resonator. It consists of a distributed Bragg reflector (DBR) with periodic, differently stressed silicon nitride and silicon dioxide multilayers implemented by plasma-enhanced chemical vapor deposition. The lower InP-based part, comprising the InP-InGaAsP bottom DBR and the active region, is grown monolithicaily using metal-organic vapor phase epitaxy.

  • 87.
    Wang, Dawei
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Lu, Chao
    Lau, Alan Pak Tao
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Adaptive Chromatic Dispersion Compensation for Coherent Communication Systems Using Delay-Tap Sampling Technique2011In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 23, no 14, p. 1016-1018Article in journal (Refereed)
    Abstract [en]

    A fast and low-complexity adaptive chromatic dispersion (CD) compensation algorithm based on delay-tap sampling technique for optical coherent systems is proposed. By generating a delay-tap plot from the signal powers after an adaptive CD equalizer, a parameter can be extracted from the delay-tap plot which can be used to estimate CD accurately. Simulation results for coherent polarization-division-multiplexed (PDM) quaternary phase-shift keying (QPSK) as well as 16-quadrature amplitude modulation (QAM) systems with various pulse shapes demonstrate that high CD estimation accuracies using relatively few data symbols can be achieved in presence of other transmission impairments.

  • 88. Wang, Q. A.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Wang, L. R.
    A low-loss Y-branch with a multimode waveguide transition section2002In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 14, no 8, p. 1124-1126Article in journal (Refereed)
  • 89.
    Wang, Qin
    et al.
    Optical Engineering Department, Acreo AB, Kista.
    Junique, Stephane
    Optical Engineering Department, Acreo AB, Kista.
    Ågren, Daniel
    Optical Engineering Department, Acreo AB, Kista.
    Noharet, Bertrand
    Optical Engineering Department, Acreo AB, Kista.
    Andersson, Jan Y.
    Optical Engineering Department, Acreo AB, Kista.
    Fabry-Perot electroabsorption modulators for high-speed free-space optical communication2004In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, no 6, p. 1471-1473Article in journal (Refereed)
    Abstract [en]

    Retroreflective modulators are key components in free-space optical communication systems between mobile platforms and users. Wide-aperture surface-normal electroabsorption modulators based on GaAs-AlGaAs quantum wells embedded in an asymmetric Fabry-Perot cavity ire designed and fabricated with a high yield. process on 10-cm wafers. It is shown that the modulator yield and its speed are improved significantly by a pixellated approach in which monolithic modulators are divided into 4-64 pixels. The fabricated 1.5 x 1.5 cm(2) devices exhibit contrast ratios of 8 dB at a driving voltage of 8 V and a modulation frequency higher than 10 MHz, which provides low noise and fast data transmission for long distance free-space optical communication.

  • 90. Wang, Zhechao
    et al.
    Dai, Daoxin
    He, Sailing
    Polarization-insensitive ultrasmall microring resonator design based on optimized Si sandwich nanowires2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 17-20, p. 1580-1582Article in journal (Refereed)
    Abstract [en]

    Bent Si sandwich nanowires are used and optimized to obtain an ultrasmall polarization-insensitive microring resonator (MRR). The used Si sandwich nanowire has a low refractive index layer between two Si layers with high refractive indexes. By optimizing the refractive index and thickness of the sandwiched layer, the bent Si sandwich nanowire becomes nonbirefringent theoretically. The designed nonbirefringent nanowire has a relatively good fabrication tolerance. By using such a nonbirefringent bent Si sandwich nanowire, an ultrasmall polarization-insensitive MRR is designed.

  • 91.
    Wang, Zhechao
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Tang, Yongbo
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Experimental demonstration of a high efficiency polarization splitter based on a one-dimensional grating with a Bragg reflector underneath2010In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 22, no 21, p. 1568-1570Article in journal (Refereed)
    Abstract [en]

    A one-dimensional grating serving both as a polarization beam splitter and a vertical coupler for silicon photonic circuits is designed, fabricated, and characterized. Bragg reflectors are employed to improve greatly the coupling efficiency. Over 50% efficiency for both polarizations are achieved experimentally, and the extinction ratio between them is also high (-20 dB).

  • 92.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Reliability study of fault-tolerant multiwavelength nonblocking optical cross connect based on InGaAsP/InP laser-amplifier gate-switch arrays1993In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 5, p. 1206-1209Article in journal (Refereed)
    Abstract [en]

    Reliability studies for a multiwavelength nonblocking optical cross connect (OXC) are presented. Calculations are based on available reliability data for commercial components as well as expected life lengths for new components and systems developed for application in the OXC. Reliability of the electronic control system is not considered here. Average OXC downtime below 2 min/year can be obtained. In general for switching systems it is required that average downtime is held below 3 min/year. As the OXC is proposed to be utilized in telecommunication in optical transport networks it is extremely important to know if this OXC exhibits reliability properties acceptable for this purpose.<>

  • 93.
    Wosinska, Lena
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS. KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Thylen, Lars
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Reliability analysis of an optical ATM switch based on wavelength routing1997In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 9, p. 336-338Article in journal (Refereed)
    Abstract [en]

    Reliability studies of a demonstrated asynchronous transfer mode (ATM) switch with all-optical packet routing are presented. Calculations are based on available reliability data for commercial components. An additional inherent redundancy is shown to improve switch availability. Our calculation results further show that a proposed multiplane switch satisfies the general reliability requirement for switching systems.

  • 94. Wu, Shengnan
    et al.
    Yan, Guofeng
    Zhou, Bin
    Lee, El-Hang
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Open-Cavity Fabry-Perot Interferometer Based on Etched Side-Hole Fiber for Microfluidic Sensing2015In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 27, no 17, p. 1813-1816Article in journal (Refereed)
    Abstract [en]

    An open-cavity fiber-optic Fabry-Perot interferometer (FPI) is designed and demonstrated, with a particular consideration for microfluidic refractive index (RI) sensing. The FPI is composed of an etched side-hole fiber (SHF) sandwiched between two single-mode-fibers. Chemical etching method is used to open up the cavity in the SHF. Experimental results show that an optimal RI sensitivity of more than 1250 nm/RI can be achieved with an open-cavity length of 38 mu m for the microfluidic RI range from 1.3400 to 1.3470. In addition, the temperature sensitivity can reach an ultralow level of 1.1 pm/degrees C. The ease of fabrication, capability for in situ measurement, and excellent performance results suggest that the proposed FPI is highly promising as an inline refractometer for temperature-insensitive label-free microfluidic detection and sensing.

  • 95.
    Xia, Li
    et al.
    Nanyang Techbological University, Singapore.
    Shum, Ping
    Nanyang Techbological University, Singapore.
    Yan, Min
    Nanyang Techbological University, Singapore.
    Wang, Yixin
    Cheng, Tee Hiang
    Nanyang Techbological University, Singapore.
    Tunable and switchable fiber ring laser among four wavelengths with ultranarrow wavelength spacing using a quadruple-transmission-band fiber Bragg grating filter2006In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 18, no 19, p. 2038-2040Article in journal (Refereed)
  • 96.
    Xiang, Yu
    et al.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Reuterskiöld-Hedlund, Carl
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yu, Xingang
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Yang, Chen
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Zabel, Thomas
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Hammar, Mattias
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Akram, Muhammed Nadeem
    University Collage of Buskerud and Vestfold.
    Performance Optimization of GaAs-Based Vertical-Cavity Surface-Emitting Transistor-Lasers2015In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 27, no 7, p. 721-724Article in journal (Refereed)
    Abstract [en]

    We report on the optimization of pnp-type verticalcavity surface-emitting transistor-lasers based on the fusion between an AlGaAs/GaAs heterojunction bipolar transistor and an InGaAs/GaAs VCSEL using an epitaxial regrowth process. It is shown how a proper design of the base region can extend the transistor active range of operation well beyond lasing threshold, thereby resulting in typical transistor laser operational characteristics including mW-range output power, mA-range base threshold current, record-low power dissipation under laser operation, and continuous-wave operation up to at least 60°C. A pronounced breakdown in the collector current characteristics in the limit of high base current and/or emitter-collector voltage accompanied by a quenching of the optical output power is interpreted as being related to quantum well band-filling.

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  • 97. Xiao, S. H.
    et al.
    Shen, L. F.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    A novel directional coupler utilizing a left-handed material2004In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, no 1, p. 171-173Article in journal (Refereed)
    Abstract [en]

    A novel directional coupler with a left-handed material (LHM) layer between two single-mode (SM) waveguides of usual material is introduced. The coupling system is analyzed with the supermode theory. It is shown that such an LHM layer of finite length can shorten significantly the coupling length for the two SM waveguides. An LHM layer with two slowly tapered ends is used to avoid the reflection loss at the ends.

  • 98.
    Yan, Min
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Analysis of surface plasmon polariton using anisotropic finite elements2007In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 19, no 22, p. 1804-1806Article in journal (Refereed)
    Abstract [en]

    The anisotropic finite-element mesh is deployed in a vector finite-element method to numerically derive surface plasmon polaritons (SPPs) more efficiently. The superiority of the anisotropic mesh lies in the fact that SPP modes, predictably, have a sharp field variation in the surface-normal direction, whereas the variation along the surface-tangent direction is comparably gentle. A case study on metallic fiber shows that the employment of anisotropic finite elements reduces the problem size by a factor of seven.

  • 99.
    Yan, Min
    et al.
    Nanyang Techbological University, Singapore.
    Shum, Ping
    Nanyang Techbological University, Singapore.
    Air guiding with honeycomb photonic bandgap fiber2005In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 17, no 1, p. 64-66Article in journal (Refereed)
  • 100.
    Yan, Min
    et al.
    Nanyang Techbological University, Singapore.
    Shum, Ping
    Nanyang Techbological University, Singapore.
    Lu, Chao
    Hole-assisted multiring fiber with low dispersion around 1550 nm2004In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, no 1, p. 123-125Article in journal (Refereed)
123 51 - 100 of 119
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